Abstract
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Objectives In Aβ brain PET imaging of AD, concomitant neocortical atrophy reduces the PET signal and as such the potential of this “hot spot” imaging technique to separate AD patients from HVs. The question of whether partial volume effect correction (PVEC) might improve the accuracy of Aβ PET has not been systematically addressed so far.
Methods We therefore analyzed florbetaben PET and MRI data obtained in a recently published Phase 0 trial [Eur J Nucl Med Mol Imaging 2011] of 10 patients with probable AD and 10 age-matched HVs. The data were co-registered and segmented (SPM5). PVEC was performed using the voxel-based modified Müller-Gärtner method (PVELab). Regional SUVs were compared between grey matter-segmented (GMS) and GMS+PVEC PET data. Mesial temporal lobe atrophy was determined by the Sheltens scale, and regional GM volumes by voxel-based morphometry.
Results PVEC had no influence on the reference region cerebellar cortex SUVs. In contrast, different neocortical SUVs in AD patients increased after PVEC to a larger extent than these in HVs. The resulting composite SUVRs increased after PVEC by 12.2±6.2 vs. 3.4±3.2% for ADs vs. HVs (p=0.001). Effect sizes (Cohen's d) for AD vs. HV separation increased by PVEC from 1.44 to 1.56 and from 0.08 to 0.69 for composite and mesial temporal cortex SUVRs. Of interest, mesial temporal cortex SUVR increase by PVEC was correlated with the Sheltens scale (r=0.92, p<0.001), and that of the composite SUVR with the composite GM volume (r=-0.71, p<0.001).
Conclusions The influence of PVEC on the florbetaben Aβ PET data is associated with the degree of brain atrophy. As a consequence, PVEC increases the power of florbetaben PET to discriminate between AD patients and HVs. To substantiate these preliminary findings, we are currently analyzing larger sample size PET data from a multi-center trial.
Research Support Bayer HealthCare (Germany